3 weeks ago I emptied fridge and freezer, unplugged unit and removed plastic backing on insideof freezer. Coils and back were completly encased in ice. Melted ice away and put unit back together. Today noticed refridge temp was above 50 degrees. Emptied freezer and removed backing and found rear of freezer/coils/wires completely iced over. Melted ice now fridge temp at 42. Why is freezer back icing up and is that what is causing temp loss in fridge.